1. Field of the Invention
This invention relates to new derivatives of 1,4-bis-styryl-benzene, a process for the preparation thereof and a use thereof as an optical brightening agent.
2. Description of the Prior Art
Up to the present time, some 1,4-bis-styryl-benzene derivatives have been proposed as an optical brightener. For example, Japanese Patent Publication No. 6715/1962 (corresponding to British Pat. No. 913,735) discloses those having free carboxyl group or its derivatives and/or nitrile group on the terminal benzene groups, Japanese Patent Publication No. 11678/1962 describes that a 1,4-bis-styryl-benzene derivative can be prepared by reacting benzylphosphonic acid, wherein the carbon atom bonded with phosphorus has at least one hydrogen atom and the p-position is not substituted by carboxyl group, or its ester with 1,4-dicarbonylbenzene compound, preferably, in an inert solvent in the presence of a proton acceptor, Japanese Patent Publication No. 580/1965 (corresponding to U.S. Pat. No. 3,076,020) discloses that 1,4-bis-styryl-benzene derivatives having free carboxyl groups or carbonyl oxygens on both the terminal phenyl groups are excellent as an optical brightener, Japanese Patent Publication No. 31870/1970 discloses those having methoxy groups or phenyl groups on both the terminal phenyl groups at the m-position or p-position, and Japanese Patent Application (OPI) No. 19875/1976 discloses those having sulfonic acid group on the central phenyl group.